[DragonQ]

are you using windows 7?

if yes this OS has huge issue with switching refresh rates.
you can try to use overlay or FSE to avoid this issue or change to a OS with a working desktop composition.

the composition is supposed to be the same as the desktop refresh rate.
and desktop refresh rate is the display refresh rate.
these composition rate mismatches are a huge problem on windows 7 and older.

the desktop refresh rate doesn't matter it is changed at the same time.

I know this is an old post but I am experiencing this issue ever since swapping my TV (could be coincidence - not sure how it could be a cause). I've tried every combination of settings I can think of but I can't get the composition rate to match the display's refresh rate. Example:

Default refresh = 50 Hz
Start watching 23.976 FPS video
Display says 23.976
Composition rate says 50

I've also seen it the other way around (display 50, composition rate 23.976). I have Kodi set to change the refresh rate as needed. I've tried D3D9, D3D11, toggling MadVR's automatic refresh rate change on and off, and other things I've forgotten. The solution offered by huhn - switching to Fullscreen Exclusive mode - doesn't work for me. The behaviour changes to this:

Default refresh = 50 Hz
Start watching 23.976 FPS video
Display says 25

I am very sensitive to stutter so there's no way this has been happening before, I'd have noticed. In every case the display refresh rate is correct, according to both MadVR and the display itself. I'm using Windows 7 on this box with an nVidia GT 430 GPU. Any ideas how to fix this or why it's started happening? The only other difference I can see is that the nVidia control panel now thinks there's a "repeater" in the HDCP chain, not sure why.